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The 9C breakup reaction was investigated in order to obtain information about the inverse reaction: 8B(p,γ)9C at astro-physical energies within the NP1412SAMURAI29R1 experiment. The 8B(p,γ)9C reaction gives a possible path to the hot pp chain pp-IV at high temperatures and away from it toward a rapid alpha-process rap-I at high temperatures and densities and therefore is important in understanding nucleosynthesis in super-massive hot stars in the early universe, including possible bypass of the 3α-process. For this experiment it was proposed to use a combination of nuclear and Coulomb dissociation measurements (on a light target Be or C and on a heavy target Pb, respectively) at energy of 160 A MeV to extract structure information, which will allow to evaluate the radiative proton capture cross section at low energies and from there the reaction rate. The current work is focused on the development of Monte Carlo simulations for Coulomb breakup mechanism of 9C as well as on the Geant4 simulations of the resulting particle trajectories through the experimental setup, including passage of the particles through the magnetic field of the SAMURAI spectrometer. [ABSTRACT FROM AUTHOR]

Using our IFIN-HH facilities: the 3 MV TandetronTM accelerator and the ultra-low background laboratory we were able to study the 4He+64Zn reaction at energies under Coulomb barrier. With these facilities, cross sections of the order of 30 nb were obtained. The thick target yields were determined through measurements of γ-ray yield followed by the decay of 67Ga (T1/2=78.28 h) in two laboratories: microBequerel (the ultra-low background laboratory) and NAG (Nuclear Astrophysics Group) where the gamma rays were detected with HPGe detectors with a relative efficiency of 120% and 100% respectively. In addition, prompt in-beam gamma-rays were detected with an HPGe detector in close proximity as long as the reaction cross section was sufficiently large for those gammas to be extracted from the target hall background. Results of the experiment are shown below. [ABSTRACT FROM AUTHOR]

The 12C(12C,α0,1)20Ne and 12C(12C,p0,1)23Na reactions have been measured from Ec.m.=2.7 MeV down to 0.8 MeV via the Trojan Horse Method o the deuteron in 14N. This range of energies is relevant in astrophysical scenarios, from superburst ignition to explosive stellar carbon burning. The deduced astrophysical S(E) factors exhibit several resonances that are responsible for a very large increase of the reaction rate at the relevant temperatures. [ABSTRACT FROM AUTHOR]

Heavy-ion fusion reactions between light nuclei such as carbon and oxygen isotopes have been studied because of their significance for a wide variety of stellar burning scenarios [1]. One important stellar reaction is 12C+12C, but it is difficult to measure in the Gamow window because of very low cross sections and several resonances occurring [2]. Hints can be obtained from the study of 13C+12C reaction. We studied 13C+12C fusion trough an activation method for energies from Ec.m.= 2.2 MeV, which is the lowest energy ever reached for this reaction (down into Gamow window), up to 5.3 MeV, using 13C beams from the Bucharest 3 MV Tandetron on thick graphite targets. Thick target yield for the 12C(13C, p)24Na reaction was determined through the measurement of the gamma ray yield following the beta decay of 24Na (T1/2=15 h) in our low and ultralow background laboratories, the latter located in a salt mine about 100 km north of Bucharest. Results of the experiments are shown. [ABSTRACT FROM AUTHOR]

The reaction cross section of the 12C+12C system is difficult to measure because of the presence of the resonances in the Gamow energy window. It has been proved that the 13C+12C reaction is a good alternative to study the behavior of the reaction cross section at energies relevant for astrophysics. We have measured it with activation and online techniques. During online measurements we were interested to determine the relative contributions of the open channels of the 13C+12C reaction. These determinations are necessary to evaluate the total fusion reaction cross section. Therefore, we have measured the γ-ray yields of proton, neutron and alpha particle evaporation channels from the resulting 25Mg compound nucleus using prompt γ-rays measurements. This complements the activation method. The irradiations took place at the 3 MV Tandetron Accelerator at IFIN-HH [1], Bucharest and the prompt gamma-rays were measured using a hyper-pure germanium detector with 100% relative efficiency, shielded with lead bricks. The energy range for the irradiation was from 4.6 up to 11 MeV (in laboratory frame), in steps of 0.2 MeV and the online measurements were performed from 6.4 up to 11 MeV. [ABSTRACT FROM AUTHOR]

We have performed experiments to check the limits of sensitivity of the activation method using the new 3 MV Tandetron accelerator and the low and ultra-low background laboratories of the "Horia Hulubei" National Institute of Physics and Nuclear Engineering (IFIN-HH). We have used the 13C+12C reaction at beam energies Elab= 6, 7 and 8 MeV. The knowledge of this fusion cross section at deep sub-barrier energies is of interest for astrophysical applications, as it provides an upper limit for the fusion cross section of 12C+12C over a wide energy range. A 13C beam with intensities 0.5-2 particleμA was provided by the accelerator and used to bombard graphite targets, resulting in activation with 24Na from the 12C(13C,p) reaction. The 1369 and 2754 keV gamma-rays from 24Na de-activation were clearly observed in the spectra obtained in two different laboratories used for measurements at low and ultralow background: one at the surface and one located underground in the Unirea salt mine from Slanic Prahova, Romania. In the underground laboratory, for Elab = 6 MeV we have measured an activity of 0.085 ± 0.011 Bq, corresponding to cross sections of 1-3 nb. This demonstrates that it is possible to measure 12C targets irradiated at lower energies for at least 10 times lower cross sections than before. β-γ coincidences will lead us another factor of 10 lower, proving that this installations can be successfully used for nuclear astrophysics measurements. [ABSTRACT FROM AUTHOR]

The elastic and inelastic scattering of 17,18O with light targets has been undertaken at 12 MeV/nucleon in order to determine the optical potentials needed for the transfer reaction 13C(17O,18O)12C . Optical potentials in both incoming and outgoing channels have been determined in a single experiment. This transfer reaction was used to infer the direct capture rate to the 17F(p,γ)18Ne which is essential to estimate the production of 18F at stellar energies in ONe novae. We demonstrate the stability of the ANC method and OMP results using good quality elastic and inelastic scattering data with stable beams. The peripherality of our reaction is inferred from a semiclassical decomposition of the total scattering amplitude into barrier and internal barrier components. Comparison between elastic scattering of 17O, 18O and 16O projectiles is made. [ABSTRACT FROM AUTHOR]

The neutron capture rate 18O(n,? )19O is important for analysis of nucleosynthesis in inhomogeneous Big Bang models and also for models of processes in massive red giant stars and AGB stars. Angular distributions of the 18O(d,p)19O reaction were measured at a deuteron energy of 16.3 MeV in NPI in Řež, Czech Republic, with the aim to determine Asymptotic Normalization Coefficients which can then be used for indirect determination of the direct contribution to the 18O(n,? )19O process. In the experiment, the gas target with 18O isotope of high purity 99.9 % was used thus eliminating any contaminating reactions. Reaction products were measured by the set of 8 ?E -E telescopes consisting of thin and thick silicon surface-barrier detectors. Angular distributions of proton transfers corresponding to 6 levels of 19O up to the 4.1093 MeV excitation energy were determined. The analysis of angular distributions in the angular range from 6 to 64 degree including also the angular distribution of elastically scattered deuterons was carried out by means of ECIS and DWUCK codes. From the determined ANCs the direct contribution to the radiative capture 18O(n,? )19O was deduced and compared with existing direct measurements. [ABSTRACT FROM AUTHOR]

We have recently developed a gas based detection system called AstroBox, motivated by nuclear astrophysics studies. The goal was to detect very low-energy protons from β-delayed p-decay with reduced beta background and improved energy resolution. The detector was tested using the β-delayed proton-emitter 23Al previously studied with a set-up based on thin double-sided Si strip detectors. The proton spectrum obtained with AstroBox showed no beta background down to ∼80 keV. The low energy (206 keV, 267 keV) proton peaks were positively identified, well separated, and the resolution was improved. [ABSTRACT FROM AUTHOR]

Decay spectroscopy is one of the oldest indirect methods in nuclear astrophysics. We have developed at TAMU techniques to measure beta- and beta-delayed proton decay of sd-shell, proton-rich nuclei. The short-lived radioactive species are produced in-flight, separated, then slowed down (from about 40 MeV/u) and implanted in the middle of very thin Si detectors. These allowed us to measure protons with energies as low as 200 keV from nuclei with lifetimes of 100 ms or less. At the same time we measure gamma-rays up to 8 MeV with high resolution HPGe detectors. We have studied the decay of 23Al, 27P, 31Cl, all important for understanding explosive H-burning in novae. The technique has shown a remarkable selectivity to beta-delayed charged-particle emission and works even at radioactive beam rates of a few pps. The states populated are resonances for the radiative proton capture reactions 22Na(p,γ)23Mg (crucial for the depletion of 22Na in novae), 26mAl(p,γ)27Si and 30P(p,γ)31S (bottleneck in novae and XRB burning), respectively. More recently we have radically improved the technique using a gas based detector we call AstroBox. [ABSTRACT FROM AUTHOR]

We have produced an intense and pure beam of 31Cl with the MARS Separator at the Texas A&M University and studied β-decay of 31Cl by implanting the beam into a novel detector setup, capable of measuring β-delayed protons and γ-rays simultaneously. From our data, we have established decay scheme of 31Cl, found resonance energies with 1 keV precision, have measured its half-life with under 1% accuracy, found its Isobar Analog State decay and by using the IMME obtained an improved mass excess for its ground state. In this contribution, a description of the used method along with selected preliminary experimental results are given and their relevance for novae nucleosynthesis discussed. [ABSTRACT FROM AUTHOR]

The 18O(p,α)15N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as 19F, 18O and 15N. In this work, a high accuracy 18O(p,α)15N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2+ resonance. Since Γ∼100-300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T∼0.5 109 K based over our new improved determination of its resonance parameters. [ABSTRACT FROM AUTHOR]

We discuss the use of one-nucleon removal reactions of loosely bound nuclei at intermediate energies as an indirect method in nuclear astrophysics. The breakup reactions are proved to be good spectroscopic tools and can be used to study a large number of loosely bound proton- or neutron-rich nuclei over a wide range of beam energies. As peripheral processes, they can be used to extract asymptotic normalization coefficients (ANCs) from which non-resonant capture reaction rates of astrophysical interest can be calculated parameter free. In this talk, we present results of a proton-breakup experiment carried out at GANIL (France) with a cocktail beam centered around 23Al at 50 MeV/nucleon. Momentum distributions of the breakup fragments, inclusive and in coincidence with gamma rays detected by EXOGAM Germanium clover array, were measured in the focal plan of SPEG energy-loss spectrometer. We present in particular the investigations of reaction rates for 22Mg(p,γ)23Al and 23Al(p,γ)24Si important for novae and X-ray bursts, respectively. [ABSTRACT FROM AUTHOR]

We have studied the β-decay of 23Al with a novel detector setup at the focal plane of the MARS separator at the Texas A&M University to resolve existing controversies about the proton intensities of the IAS in 23Mg and to determine the absolute proton branching ratios by combining our results to the latest γ-decay data. Experimental technique, results and the relevance for nova nucleosynthesis are discussed. [ABSTRACT FROM AUTHOR]

The MARS group at TAMU has developed a new experimental technique to measure very low energy protons from β-delayed proton-decay of proton-rich nuclei produced and separated with the MARS recoil spectrometer at TAMU. Recently we have investigated the β-delayed p-decays of 23Al [1], and 31Cl [2], and obtained information on the resonances in the 22Na(p,γ)23Mg and 30P(p,γ)31S reactions, respectively. These reactions are important in explosive H-burning in Novae [3]. Recently an experiment looking at the β-delayed p-decay of 20Mg was also done in order to obtain information on resonances in the 19Ne(p,γ)20Na reaction. A simple setup consisting of a telescope made of a thin double sided Si strip detector (p-detector) backed or sandwiched between two thick Si detectors (β-detectors) was designed. We studied different W1 and BB2 p-detectors made by MSL, and found that the thinner detectors with a small cell size are best to measure proton energies as low as 2-300 keV. [ABSTRACT FROM AUTHOR]

In order to understand primordial and stellar nucleosynthesis, we have studied 2H(d,p)3H reaction at 0.4 MeV down to astrophysical energies. Knowledge of its S-factor is interesting also to plan reactions for fusion reactors to produce energy. The 2H(d,p)H reaction has been studied through the Trojan Horse Method applied to the three-body reaction 2H(He,pt)H, at beam energy of 17 MeV. Once selection of protons and tritons detected in coincidence and the selection of quasi-free events, the obtained S-factor is compared with direct measurements. Such data are in agreement with the direct ones and a pole invariance test has been obtained comparing the present results with another 2H(d,p)3H THM measurements, where a different spectator particle was employed. [ABSTRACT FROM AUTHOR]

In order to understand primordial and stellar nucleosynthesis, we have studied 2H(d,p)3H reaction at 0, 4 MeV down to astrophysical energies. Knowledge of this S-factor is interesting also to plan reactions for fusion reactors to produce energy. 2H(d,p)3H has been studied through the Trojan Horse Method applied to the three-body reaction 2H(3He,pt)H, at a beam energy of 17 MeV. Once protons and tritons are detected in coincidence and the quasi-free events are selected, the obtained S-factor has been compared with direct reactions results. Such data are in agreement with the direct ones, and a pole invariance test has been obtained comparing the present result with another 2H(d,p)3H THM one, performed with a different spectator particle (see fig. 1). [ABSTRACT FROM AUTHOR]

The low-energy bare-nucleus cross section for 15N(p,α)12C is extracted by means of the Trojan-horse Method applied to the 2H(15N,α)12C)n reaction at Ebeam = 60 MeV. The astrophysical S-factor is deduced and compared to the direct data in the same energy region. A fair agreement with direct data down to 80 keV is found if energy resolution effects are taken into account. [ABSTRACT FROM AUTHOR]

The angular distributions of the 15N(3He,d)16O reaction were measured with the aim to determine the direct capture rate of the astrophysical reaction 15N(p, γ)16O by deducing asymptotic normalization coefficients (ANC). The 15N(p,γ)16O reaction is a part of the CNO cycle having importance in the nucleosynthesis of the N and O isotopes. The measurement was carried out on the cyclotron U120M of NPI CAS at the energy 25.74 MeV of 3He ions in a gas chamber containing the high purity 15N isotope. The preliminary results of corresponding spectroscopic factors and ANC's were used for the estimation of the S-factor for the direct capture 15N(p,γ)16O. Using the widths of the resonances ER = 312 and 962 keV, the total S-factor was determined within the framework of the R-matrix approach. [ABSTRACT FROM AUTHOR]

Single and double proton emissions in the 14O+4He interaction were observed with the thick target inverse kinematic method at initial energy for 14O at 32.7 MeV. It was found that the protons mainly originate from the resonance excitation of states in 18Ne. The decay of a state in 18Ne at Eex = 8.45 MeV demonstrates the features of a decay by a correlated proton pair. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method has been recently applied to the study of reactions involved in fluorine nucleosynthesis inside AGB stars. Fluorine abundance is important since it allows to constrain mixing models from the comparison of the observed fluorine abundances with the ones predicted by models. Anyway direct measurements of the cross section do not extend down to the Gamow peak, which is the astrophysically relevant energy region. In particular the study focuses on the 15N(p,α)12C and the 18O(p,α)15N reactions which can influence fluorine yield as they are part of 19F production/destruction network. [ABSTRACT FROM AUTHOR]

It was expected that γ rays from 18F and 22Na would be observed in massive One novae, but neither has been to date. The 17F(p,γ)18Ne and 22Mg(p,γ)23Al reactions may play important roles in the production and destruction of 18F and 22Na. We have determined the asymptotic normalization coefficients for 18Ne and 23Al through measurements of peripheral neutron transfer reactions in the mirror nuclear systems. We use the ANCs to calculate the astrophysical S-factors and reaction rates for these two reactions. [ABSTRACT FROM AUTHOR]

The reaction cross section of the radiative proton capture on the drip line nucleus 12N was studied at the Cyclotron Institute at Texas A&M University. We have employed the indirect Asymptotic Normalization Coefficient method to determine the direct radiative component of the astrophysical S-factor of the 12N(p,γ)13O reaction. A value of 0.31(5) keV·b was found at zero energy. Interference between direct and resonant captures leads to a further enhancement of a factor of two. The reaction was investigated in relation to the evolution of hydrogen-rich massive objects, Population III stars, because of the role that it may play in the hot pp chain nuclear burning processes occurring in such stars. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method allows for the measurements of cross sections in nuclear reactions between charged particles at astrophysical energies. The basic features of the method are discussed and recent applications are presented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The direct capture contribution for 13N(p,γ)14O has been determined more precisely with the peripheral transfer reaction, 14N(13N,14O)13C at the energy of 11.8 MeV/nucleon using the ANC technique. The updated 13N(p,γ)14O reaction rate is about 2.5 times larger than the standard REACLIB rate in the temperature range 0.1 < T9 < 0.3. The transition condition from the cold to hot CNO cycles has been determined with this updated rate. The influences incurred by this update have been investigated with two one-zone nova models. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Very accurate measurements of the half-life, 3.8755(12) s, and the branching ratio, 0.5315(12), are reported for the superallowed 0+ → 0+ β-decay of 22Mg. The precision in the branching ratio was achieved by the efficiency calibration of an HPGe detector to 0.15% precision for γ-ray energies between 50 and 1400 keV. The ft-value extracted from the measurement, corrected for small calculated radiative effects is Ft=3071(9) s. With this measurement, we open up a new series of superallowed emitters with Tz = -1 to precision measurements. This series will permit direct tests of the calculated nuclear-structure-dependent correction terms essential to the determination of the vector coupling constant, GV, and of Vud, the up-down quark-mixing element of the Cabibbo-Kobayashi-Moskawa (CKM) matrix. As the top row of the CKM matrix currently fails the unitarity test by more than two standard deviations, measurements to improve the precision with which Vud is known are of paramount importance. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]